Sometimes, we give a correct answer to a question, and then later, the OP changes the question, so that the answer does not match the question any more. Later, some careless readers come in and vote down those answers that used to be correct but do not match the question any more because the question was edited.
We cannot keep "polling" all the questions that we have ever answered to see if they are changed, so what is the best way to deal with these stupid down-votes?